'Free tank'....

If you already have the hydroton...sure. If you want to 'save' the hydroton for your plants....and If you got the $ to buy something....I'd consider bioiballs or PVC shavings.

The 'organic feed' issue....has been kicked around a lot, on 'what it 'is' and/or should 'be'...? Some say it's OK to have 'land animals' in it for protein....others say that's not natural...it should be seafood based protein ( I guess piranhas eat cows, when they get in the water... )

Then there is the issue of using 'plants' for protein....most soybeans and 'stuff' have been....'Monsanto-ized'... ...